1. Field
Disclosed herein is a composite article with magnetocalorically active material and to methods for producing a composite article with magnetocalorically active material.
2. Description of Related Art
The magnetocaloric effect describes the adiabatic conversion of a magnetically induced entropy change to the evolution or absorption of heat. Therefore, by applying a magnetic field to a magnetocaloric material, an entropy change can be induced which results in the evolution or absorption of heat. This effect can be harnessed to provide refrigeration and/or heating.
In recent years, materials such as La(Fe1-aSia)13, Gd5(Si, Ge)4, Mn (As, Sb) and MnFe(P, As) have been developed which have a Curie Temperature, Tc, at or near room temperature. The Curie Temperature translates to the operating temperature of the material in a magnetic heat exchange system. Consequently, these materials are suitable for use in applications such as building climate control, domestic and industrial refrigerators and freezers as well as automotive climate control.
Magnetic heat exchange technology has the advantage that magnetic heat exchangers are, in principle, more energy efficient than gas compression/expansion cycle systems. Furthermore, magnetic heat exchangers are environmentally friendly as ozone depleting chemicals such as CFC's are not used.
Consequently, magnetic heat exchanger systems are being developed in order to practically realise the advantages provided by the newly developed magnetocaloric materials. Magnetic heat exchangers, such as that disclosed in U.S. Pat. No. 6,676,772, typically include a pumped recirculation system, a heat exchange medium such as a fluid coolant, a chamber packed with particles of a magnetic refrigerant working material which displays the magnetocaloric effect and a means for applying a magnetic field to the chamber.
Further developments of these systems have been directed towards optimizing the composition of the magnetocaloric material so as to increase the entropy change and to increase the temperature range over which the entropy change occurs. This enables smaller applied magnetic fields to be used to achieve sufficient cooling and a stable refrigeration cycle to be achieved over a larger temperature range.
These measures aim to simplify the design of the heat exchange system since smaller magnetic fields can be produced by a permanent magnet rather than an electromagnet or even a superconducting magnet.
The magnetic refrigerant working material may also be provided in the form of a composite. For example, U.S. Pat. No. 6,826,915 discloses a regenerative bed comprising a magnetic refrigeration material including a binder comprising a metal or alloy of high ductility and a magnetocaloric material of the NiAs-type.
However, further improvements are desirable to enable a more extensive application of magnetic heat exchange technology.